Out of 64 patients with rheumatoid arthritis (RA), 42 were treated with D-penicillamine (D-Pa) for more than 6 months and 22 for less than 6 months. The latter patients were excluded from the evaluation of the effect. The former patients were treated with doses of 600-1 250 mg daily for 6-41 months (mean 16.8). The clinical effect was retrospectively assessed as favourable in 24 patients, 12 did not respond and the effect could not be assessed in 6. The clinical assessment was supported by significant reductions of ESR and orosomucoid. Adverse reactions, although rarely serious, led to withdrawal of the drug in 25 (39%) of the 64 patients. It is concluded that D-Pa is a valuable drug in the treatment of severe RA.